1. Field of the Invention
This invention relates to compositions that are useful for forming artificial fingernails and protective coatings on human fingernails. In particular, the present invention comprises self-curing compositions which polymerize rapidly at ambient temperatures and are resistant to yellowing, when applied over human fingernails to protect, adorn, extend, and/or decorate them.
2. Prior Art
The prior art discloses a variety of useful, self-curing compositions that can be applied to human fingernails for the purpose of forming an artificial fingernail. In general, these compositions are two-part systems which consist of a liquid portion (herein referred to as a binder) and a powder portion (herein referred to as a polymeric filler). In particular, such compositions are described in U.S. Pat. Nos. 4,104,333, 4,229,431, 4,260,701, 4,626,428, 4,669,491, 4,708,866, 4,718,957, and 4,871,534.
The liquid binders as described therein comprise the following ingredients:
(a) a monomeric acrylate or methacrylate ester such as ethyl methacrylate, tetrahydrofurfuryl methacrylate, methoxyethyl methacrylate, methoxyethoxyethyl methacrylate, and others, PA1 (b) a di-, tri-, or multi-functional acrylate or methacrylate ester such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, trimethylolpropane trimethacrylate, and others, and PA1 (c) a tertiary amine accelerator such as N,N-dimethyl-p-toluidine. PA1 (a) a finely divided polymeric methacrylate, such as poly(ethyl methacrylate) or copolymeric methacrylate, such as a 70:30 molar ratio comprising poly(ethyl-co-methyl methacrylate), and PA1 (b) an organic peroxide polymerization initiator such as benzoyl peroxide. PA1 (a) one or more monomeric methacrylate esters, PA1 (b) optionally and preferably, one or more di-, tri-, or multi-functional methacrylate esters, PA1 (c) an unsaturated or saturated alcohol, and PA1 (d) a tertiary amine accelerator PA1 (a) a finely divided polymer, and PA1 (b) an organic peroxide polymerization initiator. PA1 (a) from about 10 percent to about 95 percent of a methacrylate monomer including, but not limited to, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, tert-butyl methacrylate, methoxyethoxyethyl methacrylate, ethoxyethoxyethyl methacrylate, benzyl methacrylate, phenethyl methacrylate, and combinations thereof; PA1 (b) optionally and preferably, from about 1 percent to about 50 percent of a di-, tri-, or multi-functional methacrylate crosslinker including, but not limited to, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, poly(ethylene glycol) dimethacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,12-dodecanediol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, and combinations thereof; PA1 (c) from about 1 percent to about 50 percent of an unsaturated or saturated alcohol compound including, but not limited to, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, isopropyl alcohol, propylene glycol, 1,4-butylene glycol, neopentyl glycol monomethacrylate and combinations thereof, and; PA1 (d) from about 0.1 percent to about 5.0 percent of a tertiary amine polymerization accelerator, selected from the group including, but not limited to, N,N-dimethyl-p-toluidine, N,N-dihydroxyethyl-p-toluidine, N,N-dimethyl aniline, and 4-(dimethylamino)phenethyl alcohol (U.S. Pat. No. 4,284,551). PA1 (a) from about 95 percent to about 99.9 percent of a finely divided polymer selected from the group including, but not limited to, poly(ethyl methacrylate), poly(methyl methacrylate), poly(ethyl-co-methyl methacrylate), poly(butyl methacrylate), poly(methyl-co-butyl methacrylate), poly(vinyl acetate), poly(vinyl butyral), poly(ethyl-co-butyl methacrylate), PA1 (b) from about 0.1 percent to about 5.0 percent of an organic peroxide polymerization initiator, preferably benzoyl peroxide.
Optionally, the liquid binders may contain polymerization inhibitors (such as methyl ether of hydroquinone or BHT), dyes, and ultraviolet light stabilizers.
The polymeric filler portion of the prior art compositions generally comprise the following ingredients:
Optionally, the polymeric filler portions may contain pigments (such as titanium dioxide), secondary polymers (such as poly[vinyl acetate]) and flow modifiers (such as fumed silica).
The procedure of forming an artificial fingernail in situ (i.e., on a human fingernail) is an exacting art which is performed by trained and licensed personnel. An artist's-type brush is first dipped in a reservoir containing the liquid binder portion in order to wet the brush fibers. The brush tip is then transferred to a reservoir containing the polymeric filler portion in such a way as to allow the wetted brush to absorb sufficient powder to form a dough-like mass at the end of the brush. This dough-like mass is then transferred to the surface of the human fingernail and subsequently shaped with the brush to form the desired coating and/or artificial fingernail extension. Forms are often attached to the end of the fingernail to provide a surface on which to apply the extension in order to extend the length of the artificial nail beyond the length of the natural nail.
In the process of mixing the liquid binder with the polymeric filler, a free-radical polymerization process is initiated by the dissolution of the organic peroxide (provided by the polymeric filler) in the liquid binder. As the organic peroxide dissolves in the liquid binder, it produces free-radicals through interaction with the tertiary amine accelerator already present in the binder. A proper balance of initiator and accelerator, in addition to liquid binder and polymeric filler, allows sufficient working time to shape the dough-like mass into the desired form, yet causes polymerization (solidification) to ensue within a reasonable length of time. It is desirable for the mass to begin the polymerization process within from about 120 seconds to about 360 seconds from the time of initial mixing of the liquid binder and the polymeric filler. The ideal and preferred polymerization time is from about 180 seconds to about 300 seconds from the time of initial mixing. If the time for polymerization is too long, there is an increased likelihood of damage to the surface of the coating before it is fully hardened, and the added inconvenience of a long waiting time for drying. If polymerization occurs too quickly, the coating may be hardened before application is completed.
The time of onset of polymerization can be controlled by varying the amounts of the organic peroxide (generally contained and dispersed within the polymeric filler portion of artificial fingernail compositions) and tertiary amine (found in the liquid binder portion). By increasing the levels of both organic peroxide and tertiary amine, a more rapid polymerization may be achieved. However, excess organic peroxides and tertiary amines are believed to cause the production of chromogenic substances which result in the discoloration of artificial fingernails (often referred to as "yellowing"). Thus, a practical limit on the highest amounts of both organic peroxides and tertiary amines is reached whereby further decrease in polymerization time is accompanied by an increase in polymer discoloration.
It would thus be advantageous to provide a rapid-polymerizing, yet non-yellowing artificial fingernail composition, which utilizes the same application methods as the prior art compositions.
It would also be advantageous to provide an artificial fingernail composition capable of polymerizing in from about 120 seconds to about 360 seconds without the yellowing associated with the heretofore required high organic peroxide and tertiary amine concentrations utilized in the prior art.